Which drug is commonly used to decrease AV node excitability in cases of atrial flutter and fibrillation?

Cardiac digitalis, commonly known as digoxin, is a medication frequently used to decrease the excitability of the atrioventricular (AV) node in individuals with atrial flutter and atrial fibrillation. It works by increasing vagal tone and acting on the AV node to slow conduction and reduce the heart rate. This is particularly helpful in the management of atrial fibrillation, where controlling the ventricular rate is essential.

In the context of atrial flutter or fibrillation, decreasing the AV node's excitability helps to prevent rapid and irregular heart rhythms, which can lead to inadequate filling of the ventricles and potentially result in heart failure or other complications. Digoxin's specific mechanism allows it to selectively target these issues, making it a notable option for such conditions.

Other drugs listed serve different purposes; for example, procainamide is primarily used as an antiarrhythmic agent but does not specifically target the AV node in the same way digoxin does. Lidocaine is typically used for ventricular arrhythmias, and aspirin is an antiplatelet agent, which does not have any direct effects on heart rhythm management.